Chest
Volume 83, Issue 2, February 1983, Pages 215-220
Journal home page for Chest

Total Resistance and Reactance in Patients with Respiratory Complaints with and without Airways Obstruction

https://doi.org/10.1378/chest.83.2.215Get rights and content

A comparison was made of the frequency dependence of total respiratory resistance, (Rrs), and reactance (Xrs), determined by a forced oscillation technique in 442 healthy subjects and in 126 patients with respiratory complaints, with or without slight airways obstruction. The comparison was performed by means of a discriminant analysis. The latter demonstrated that the Rrs and Xrs data, measured between 8 and 24 Hz, of patients differ from those of healthy subjects primarily by a decrease of Rrs with frequency associated with more negative Xrs (and thus with an increase in resonant frequency). This probably also applies to patients with more advanced airways obstruction. The addition of the FEV1 values to the analysis provides only a small amount of independent information. The forced oscillation technique thus appears to be a sensitive tool to separate healthy subjects (smokers and nonsmokers) from patients with respiratory complaints associated or not with a reduced FEV1.

Section snippets

Technique

The technique has been described in detail in another publication.8 The seated subject supports his cheeks with his hands and breathes quietly via a screen pneumotachograph through a low impedance side tube; a bias flow reduces the CO2 build-up at the mouth. Simultaneously, a pseudo-random noise pressure signal, containing all harmonics of 2 Hz to 24 Hz with a peak-to-peak amplitude smaller than 0.2 kPa, is applied at the mouth by means of a loudspeaker. Mouth pressure and airflow, recorded by

Total Respiratory Resistance (Rrs) and Reactance (Xrs) vs Frequency (f) Curves

The mean course of Rrs and Xrs vs f in the investigated samples are shown in Figures 1 and 2.

Discriminant Analysis

To investigate which factor best separates healthy subjects from patients with minor complaints with or without slight reductions of FEV1 (samples B and C), first an analysis was performed on sample A (healthy subjects) and the combined samples B and C. Among the investigated ten factors (mean Rrs and Xrs, first four derivatives of Rrs and Xrs), only five turned up to be significant ( Rrs¯, Rrs(1)

DISCUSSION

In patients with manifest COPD, the Rrs and Xrs vs f curves are usually clearly altered:1, 2, 3, 49 there is a frequency dependence of Rrs and the resonant frequency is increased. In milder cases, the alterations of the Rrs and Xrs-f curves may be less pronounced and resemble the tracings sometimes met in presumably healthy subjects. Of course, one may wonder if some of the latter subjects, without complaints and with normal spirographic values, are not in an early stage of a disease, which

REFERENCES (12)

  • LandserFJ et al.

    Normal values of total respiratory resistance and reactance determined by forced oscillations: influence of smoking

    Chest

    (1982)
  • GrimbyG et al.

    Frequency dependence of flow resistance in patients with obstructive lung disease

    J Clin Invest

    (1968)
  • MichaelsonED et al.

    Pulmonary mechanics by spectral analysis of forced random noise

    J Clin Invest

    (1975)
  • KjeldgaardJM et al.

    Frequency dependence of total respiratory resistance in early airway disease

    Am Rev Respir Dis

    (1976)
  • HayesDA et al.

    Detection of respiratory mechanical dysfunction by forced random noise impedance parameters

    Am Rev Respir Dis

    (1979)
  • PeslinR et al.

    Impédance mécanique thoracopulmonaire chez des sujets fumeurs et non fumeurs

    Bull Europ Physiopath Respir

    (1981)
There are more references available in the full text version of this article.

Cited by (132)

  • Oscillometry for lung function testing

    2018, Lung Function Testing in the 21st Century: Methodologies and Tools Bridging Engineering to Clinical Practice
  • Oscillometry for lung function testing

    2018, Lung Function Testing in the 21st Century: Methodologies and Tools Bridging Engineering to Clinical Practice
View all citing articles on Scopus

Supported by a grant from the Commission of the European Communities.

Manuscript received April 29; revision accepted July 30.

View full text